Implantable medical devices are used to deliver neurostimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, incontinence, sexual dysfunction, obesity, or gastroparesis. Neurostimulation may involve delivery of electrical pulses via one or more leads that include electrodes located proximate to the spinal cord, pelvic nerves, or stomach, or within the brain of a patient.
Prior to implantation of a neurostimulation device, the patient may engage in a trial period, in which the patient receives an external trial neurostimulation device on a temporary basis. An external trial stimulator screener, for example, may be coupled to one or more implanted leads via a percutaneous lead extension. The trial neurostimulation permits a clinician to observe neurostimulation efficacy and determine whether implantation of a chronic neurostimulation device is advisable.
Specifically, the trial neurostimulation period may assist the clinician in selecting values for a number of programmable parameters in order to define the neurostimulation therapy to be delivered to a patient. For example, the clinician may select an amplitude, which may be current- or voltage-controlled, and pulse width for a stimulation waveform to be delivered to the patient, as well as a rate at which the pulses are to be delivered to the patient. In addition, the clinician also selects particular electrodes within an electrode set on a lead to be used to deliver the pulses, and the polarities of the selected electrodes. A group of parameter values may be referred to as a program in the sense that they drive the neurostimulation therapy to be delivered to the patient.
The clinician may make notations describing a number of programs and feedback perceived from the patient regarding the perceived efficacy of each program. The clinician may then select the “best” program, e.g., a program that the notations indicate is better in terms of clinical efficacy versus side effects than other programs tested.